MIPS: JZ4740: GPIO: Use shared irq chip for all gpios

Currently there is one irq_chip per gpio_chip with the only difference
being the name. Since the information whether the irq belong to GPIO
bank A, B, C or D is not that important rewrite the code to simply use
a single irq_chip for all gpio_chips.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
To: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2182/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>